Intro.

I have been focusing on so many flagships that sometimes overlook interesting budget releases. I still get a lot of those for review, but not everything catches the attention, especially due to my limited time. I have reviewed Alpha & Delta debut AD01 about 3 years ago, and remember being quite impressed with a sound and a build quality, especially build quality. New D6 caught my attention because right away I noticed a non-detachable cable and 3-year warranty, indicating that AD has a lot of confidence in durability of their design. But the biggest surprise came when I started to listen to it.

While they have a nice mid-forward sound out of the box, when I used Veritas coupler to measure FR, I noticed a significant boost in low end response. That’s not what I heard when listening to D6 with my ears. Looking closer, I realized that while I pushed these IEMs into a coupler for measurement, the core of eartip slid all the way to the back, covering the front vent. That’s how I discovered this “easter egg” trick to turn D6 into dual sound signature, controlled by eartip placement on the nozzle. It was my “Eureka” moment, and I even went back to check other D6 reviews, though nobody mentioned that.

That sealed the deal for me to start working on the review, to share with my readers not only about these iems in general, but also about how you can “flip” the bass boost switch depending on eartip placement. Here is more about it.

Unboxing and Accessories.

Packaging here has a bit of an “old school” feeling with a clear display window so you can preview IEMs even before opening the box. It’s a nice touch, considering many manufacturers today have a solid packaging box with some artwork print on the top. D6 was securely wedged in a foam cutout, with all the accessories underneath.

Accessories include a pair of ear guides (that’s an old school for sure) which might come handy if you want to wear D6 wire up, a shirt clip, a pair of foam eartips (non-Comply), and 9 pairs of silicone eartips in various shapes (3 sets of S/M/L, one silicone rounded, one silicone with a more cone-shape, and one hybrid with thicker core). Those are basic accessories, but to take it to the next level, AD included a leather case and a leather cable wrap. I have seen some budget iems with a leather case, but those are usually pleather glued cases. Here it feels and smells like a genuine quality leather, both a case and a cable wrap.

Design.

In the heart of the D6 is a 10mm dynamic driver inside of a very lightweight metal bullet shell housing with a dual air chamber acoustic design. They even went as far as licensing technology behind HDSS (high definition sound standard) to ensure low distortion, higher clarity, and improved soundstage expansion. The back (faceplate) of D6 shells has AD logo and HDSS label to show the licensed tech inside.

Top of the shell has a vent for the back venting of the driver, while the nozzle of the shell has a front venting at the bottom. The front vent, which is easy to miss, is the key to its unique dual sound sig. In theory it wasn’t designed to have dual signature, so you can refer to this as a mod. But it’s so easy to control that I consider this to be almost like a feature due to a very noticeable sound difference. The nozzle has a mesh cover and a lip at the tip, to protect eartips from sliding off, followed by what appears to be a notch which works as a stopper to keep the front vent open.

So, when you push the eartip in, it stops after that notch, leaving the vent open. But if you slide it further to the back of the nozzle – it closes/covers the front vent. I will refer in my sound analysis to sound with vent open and closed. Just one thing you must keep in mind, when closing the front vent, you are not only controlling the bass response of the sound, but can also introduce a driver flex (that click when you insert the iem in your ears) because you are blocking front air escape. That could be fixed by tip rolling, to relax the seal which eliminates driver flex and reduces the bass slam when vent is closed.

The cable is attached to the shell at the bottom and has a flexible rubber strain relief. That rubber boot/strain relief has L/R imprinted on the inside, but it’s nearly impossible to see that marking. Instead, the left side strain relief has a bump which is easy to feel, being an indicator of the left side since shells are identical otherwise.

Cable is truly high end, with 8 braided SPC (silver plated copper) conductors. Yes, it’s a pity that cable is not detachable because it’s high quality and would have been great to use with other iems. I can only guess that due to dual air chamber design, the detachable socket would have been sticking out too far, and perhaps AD tried to avoid that. But keep in mind, they have a lot of confidence in reliability of these IEMs, thus include 3-year warranty. So, with cable, you have 4 braided conductors on each side going down to a nice cylindrical y-splitter with Alpha & Delta logo, and then continue in a neat 8-wire braid down to 3.5mm single ended TRS connector.

Wires are soft and have a nice clear shielding, and even with 8 wires in the braid, the cable is still flexible. There is a little bit of microphonics, but it’s not as bad and you have included shirt clip if it bothers you. The L-shaped headphone plug is nice, with rubbery housing and metal boot, and it has a very cool spring strain relief. The only wishful thinking considering multi-core design – too bad it’s single ended and not balanced terminated, though I do have to remind myself this is still a premium cable with an under $100 product. One thing that was missing here is a chin-slider which would have been a good idea, not as much when you wear wires down, but when you attempt to wear them up. You can probably make a DIY chin slider with a rubber band.